1. Field of the Invention
The present invention relates generally to the fields of physics and chemistry. More specifically, the present invention relates to a new process which can deposit well adhered ultra smooth diamond films on metals with film roughness of 14 nanometers and hardness as high as 90% of that of a natural diamond crystal.
2. Description of the Related Art
The field of nanocrystalline diamond and tetrahedral amorphous carbon films has been the focus of intense experimental activity in the last few years for applications in field emission display devices, optical windows, and tribological coatings. Nanocrystalline chemical vapor deposited (CVD) diamond films have been synthesized from a variety of plasma feedgases including fullerenes or methane in argon (with and without hydrogen), as well as from methane/nitrogen plasmas.sup.1-3.
It is generally agreed that the diamond grain size in these materials ranges from 3 to 30 nm and that the deposited films are smooth with a typical surface roughness of around 40 nm. Another class of carbon-based films called tetrahedral amorphous carbon can be grown by pulsed laser deposition.sup.4, cathodic arc deposition.sup.5, and ion deposition methods.sup.6. The sp.sup.3 content in the tetrahedral amorphous carbon films can be as high as 85% and they can be made stress-free by thermal annealing.sup.4.
The choice of substrate used in the studies mentioned above has been silicon typically. For metals, however, the thermal expansion mismatch between the diamond film and substrate gives rise to thermal stress which often results in delamination of the film.sup.7. To avoid this problem in conventional chemical vapor deposited diamond, low substrate temperatures (&lt;700.degree. C.) have been used, often with the incorporation of oxygen or carbon monoxide to the feedgas mixture.sup.8. Conventionally grown chemical vapor deposited diamond films are also rough and would require post-deposition polishing for most applications.
While nanocrystalline chemical vapor deposited diamond films have been well-characterized with respect to their structure and field-emission properties, surprisingly little information is published on the deposition of nano-structured diamond coatings on metals in which the issues of interfacial adhesion and film toughness are relevant for tribological applications.
The prior art lacks an effective means for deposition of well-adhered, smooth nano-structured diamond films on metals for various tribological applications. The present invention fulfills this long-standing need and desire in the art.